Biochemistry

Cysteine. An enzymatic redox reaction due to the presence of a reactive SH group in cysteine is easily carried out in the tissues of the body. In this case, cystine is formed. The property of this amino acid to oxidize gives it protective and radioprotective properties. In the presence of cysteine, the intensity of oxidative processes in lipids and proteins decreases, the body's resistance to ionizing radiation increases, and the quality of the drugs taken stabilizes. With the participation of two cysteine residues in the polypeptide chains, disulfide bonds are formed that determine the biological activity or functional properties of the proteins in the food composition. Disulfide bonds play a particularly important role in wheat proteins, since they impart elastic properties to gluten. Three amino acids - arginine, glycine and methionine - are involved in the synthesis of creatine compounds, through which continuous resynthesis of the ATP macroerg occurs in muscle tissue. With the participation of creatine in the body of humans and animals, creatine-phosphate is formed, which, as necessary, gives its phosphate group to ADP molecules, turning into creatinine-. Creatine + ATP — » Creatine Phosphate + ADP Creatine and cyclic creatinine are part of the meat extract, their ratio depends on the pH of the medium and temperature. So, when meat is heated in an acidic environment, creatinine predominates in the extract. Amino acids citrulline and ornithine participate together with arginine in the urea formation cycle in humans and animals. Glutamic and aspartic acids play a fundamental role in the metabolism of living organisms. They participate in the processes of cleavage, synthesis, and transfer, often in the form of amides. Glutamine, for example, is the main form of ammonia transfer in human blood and, together with aspartic acid, serves as a precursor to the pyrimidine ring of nucleotides. The reactions of decarboxylation of glutamic acid with the formation of y- aminobutyric acid, which belongs to the group of mediators, play an important role in the metabolism in the brain and nerve tissue. The exchange of proline, which is synthesized from it as a result of reduction by proline dehydrogenase, is closely related to the exchange of glutamic acid. Proline plays an important role in the formation of the structure of collagen and wheat gluten proteins, causing bends in polypeptide chains. In collagen, along with proline, 4-hydroxyproline and 5 -hydroxylysine are found, formed due to the oxidation of the corresponding amino acids after inclusion in the protein. The presence of oxyproline in meat and sausages affects their quality and is taken into account when evaluating it. 47